(57) By drying sludge in a drying plant of the drum type (1) a heating by means of a burner
(2) is carried out. To ensure that the sludge may dry in a traditional rotary drier
of the type, which e.g. is used for the manufacturing of green pellets, draining of
the sludge to a dry matter content of approximately 15-35% is first carried out. The
drained sludge (3) is subsequently mixed with an inflammable material (5) which has
a dry matter content down to 30-40% in a mixer (4). Hereby, a crumbled composite product
(6) is obtained which is conveyed to the drying drum (1) (at 10) in the immediate
vicinity of the burner (2). Hereby, a substantially momentary evaporation of the water
content is obtained and the composite product is conveyed pneumatically and mechanically
through the drier (1), and may be separated in a cyclone (13), whereafter a grinding
and pelletizing may be carried out in order to manufacture fuel pellets. These pellets
may be burned together with coal in large combustion plants which are provided with
smoke purifying equipment for removal of possible heavy metals.
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